case study: using mets as a dip to navigate archived websites leslie myrick, nyu mets opening day /...
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Case Study: Using METS as a DIP to Navigate Archived Websites
Leslie Myrick, NYUMETS Opening Day / UKThe British Library 12 July, 2004
Political Communications Web Archive Project (PCWA)
• Under auspices of CRL and Mellon• Participants: Cornell University, Stanford
University, UT Austin, NYU• Focus: SE Asia, Sub-Saharan Africa, Latin
America, Western Europe• Radical political born-digital “ephemera” • Content: Internet Archive (.arc files)
Today’s Topics
• Background: challenges of web archiving
• How METS can address some of these challenges
• How to construct a METS website object
• How METS instances can be used to control and navigate website objects in an archive
Basic METS Recipe
• fileSec• structMap• structLink • dmdSec• amdSec
Web Archiving Challenges I:Definition and Taxonomy
• Definition of the object “website” and its boundaries– what to do with external links? “near files”?
• Complex nature of website structure– which structure?
• Complex “symphonic” nature of a web page itself
<METS:fileSec>
File inventory<METS:fileSec> <METS:fileGrp> <METS:file ID="FID18" MIMETYPE=" text/html" ADMID="ADM1"> <METS:FLocat LOCTYPE="URL" xlink:href="www.apgawomen.org/" /> </METS:file> <METS:file ID="FID113" MIMETYPE="text/html” ADMID="ADM2">
<METS:FLocat LOCTYPE="URL" xlink:href="www.apgawomen.org/officers.htm" /> </METS:file> <METS:file ID="FID120" MIMETYPE="text/html” ADMID="ADM3">
<METS:FLocat LOCTYPE="URL" xlink:href="www.apgawomen.org/calender.htm" /> </METS:file> <METS:file ID="FID154" MIMETYPE="text/html" ADMID="ADM4">
<METS:FLocat LOCTYPE="URL" xlink:href="www.apgawomen.org/newsarchives.htm" /> </METS:file> <METS:file ID="FID1059" MIMETYPE="text/html" ADMID="ADM5">
<METS:FLocat LOCTYPE="URL" xlink:href="www.apgawomen.org/home.htm" /> </METS:file> ,,, </<METS:fileGrp></METS:fileSec>
<METS:structMap>
<html><head><title>index</title><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"></head><body bgcolor="#000000"><table width="100%"> <tr><td> <div align="center"><object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=4,0,2,0" width="700" height="150"> <embed src="notjust.swf" quality=high pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" width="700" height="150"> </embed> </object></div> </td></tr></table><table width="100%"> <tr> <td> <div align="center"><object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=4,0,2,0" width="600" height="64"> <embed src="apgawnew.swf" quality=high pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" width="600" height="64"> </embed> </object></div> </td> </tr></table><p> </p><div align="center"> <table width="85%"> <tr><td> <div align="right"><a href="home.htm"><img src="enterarrow.gif" width="80" height="27" border="0"></a></div> </td></tr> </table></div></body></html>
METS structMap view of an HTML page
HTML wrapper around embedded files and hyperlinks:<div> for the HTML page
<fptr> <par>
<area>for page + each embedded “parallel” element -- .css, .js, images etc. (with ID-IDREF to file ID in fileSec)
<div> for each (internal) hyperlinked page
<METS:div DMDID="DM1" TYPE="web page" ID="page18" LABEL="http://dlibdev.nyu.edu/webarchive/metstest/www.apgawomen.org/
index.html "> <METS:fptr> <METS:par>
<METS:area FILEID="FID18"/> [index.html ] <METS:area FILEID="FID1036"/> [notjust.swf] <METS:area FILEID="FID1043"/> [apgawnew.swf] <METS:area FILEID="FID1075"/> [enterarrow.gif] </METS:par>
</METS:fptr> <METS:div TYPE="hyperlink" ID="LINK1" LABEL="home">
<METS:fptr> <METS:area BEGIN="000" BETYPE="BYTE" END="111"
FILEID="FID18"/> </METS:fptr> </METS:div>
METS structMap for a Website
Flattened logical tree hierarchy:
<div> entry page, “index.html”
<div> each HTML page
<div> each hyperlink to a page internal to the site
METS DB view of site structure
DB View of Page Structure
DB View of Embedded Elements
<METS:structLink>
Mapping Hyperlink Structure
<div>s (via div ID) in structMap cross-referenced to <smLink>s in structLink:
<METS:structLink> <METS:smLink from="LINK1" to="page1059"
xlink:title="home"/> <METS:smLink from="LINK2" to="page113"
xlink:title=”officers"/><METS:smLink from="LINK3" to="page102"
xlink:title=”calendar"/></METS:structLink>
Web Archiving Challenges II: Extracted vs Human-catalogued
Metadata• Lack of influence over content production• Questionable embedded metadata from producers
of web pages, e.g. <title> <meta> tags– Technical metadata is “safe” because it can be
programmatically extracted from the file itself– Do we want to take descriptive metadata wholesale
from <title>, <meta> tags? – Really?
The Case of the Purloined Metadata
The Case of the Purloined Metadata, continued
<snip>
<HTML><!-- saved from url=(0041)http://www.sport.de/spart/sk1/ski006.php3 --><HEAD><TITLE>Bienvenue sur le site de Front Social</TITLE><META CONTENT="text/html; charset=windows-1252" HTTP-EQUIV="Content-Type"><META CONTENT="Sport sports Baseball Basketball Beach-Volleyball Bob Boxen Bundesliga Bundesligavereine Championsleague DEL DFB DFB-Pokal Eishockey Ergebnisse Europameisterschaft Europapokal Fernsehen Football Formel1 Formel3 Fußball Golf Hallenmasters Handball Hockey Inline-Skating Leichtathletik Motorbike Motorrad Motorsport Nationalmannschaft NBA NFL NHL Reiten Rodeln Schwimmen Skifahren Skispringen Snowboard Sportarten Sportnachrichten Surfen Tennis Tischtennis Turniere Uefa-Cup US Open Vereine Volleyball Wassersport WBA WBC WBO Weltmeisterschaft Weltrangliste Wimbledon Fußball Motorsport Radsport Volleyball Sport Eishockey Skisport Boxen Handball Leichtathletik Pferdesport Schwimmen" NAME="keywords"> <META CONTENT="Sport Sportnachrichten Sportvereine Ergebnisse Tabellen Ranglisten Bundesliga DEL Formel 1 Tennis" NAME="description"> <META CONTENT="thu, 30 mar 2000 12:00:00 GMT" HTTP-EQUIV="date"> <SCRIPT language="JavaScript" SRC="sport_fichiers/sidiscript.js"> <SCRIPT language="JavaScript"><!--var on = "/ima/pfeil_weiss2.gif";var off = "/ima/pfeil_weiss.gif"; </snip>
Whence Web Archive Metadata?
• Programmatically extractable metadata provided by crawlers – Found in logs, .arc + .dat files, files themselves
• Balance to be struck between automated metadata extraction and human cataloguing (especially for descriptive metadata)
<METS:dmdSec>
Case study: Metadata from an Alexa .arc
• Typical Alexa / IA SIP = .arc and .dat files along with byte offset .ndx file– IA .arc = 100 MB .gz archive file packed with
files from web crawl along with server’s HTTP response headers for each file.
Typical IA .arc snippet
<snip>[ crawler’s file header]http://www.apgawomen.org:80/calender.htm 63.241.136.203 20030417223125 text/html 2570
[http headers]HTTP/1.1 200 OKDate: Thu, 17 Apr 2003 21:35:43 GMTServer: Apache/1.3.27 (Unix) FrontPage/5.0.2.2510Last-Modified: Sun, 26 Jan 2003 04:05:37 GMTETag: "3b01d2-8fb-3e335e91"Accept-Ranges: bytesContent-Length: 2299Connection: closeContent-Type: text/html
[file itself]<html><head><title>calender</title><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"></head><body bgcolor="#FFFFFF"> </snip>
What is extractable (dmdSec)?
HTTP/1.1 200 OKDate: Thu, 17 Apr 2003 21:35:43 GMTServer: Apache/1.3.27 (Unix) FrontPage/5.0.2.2510Last-Modified: Sun, 26 Jan 2003 04:05:37 GMTETag: "3b01d2-8fb-3e335e91"Accept-Ranges: bytesContent-Length: 2299Connection: closeContent-Type: text/html
<html><head><title>calender</title><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"></head><body bgcolor="#FFFFFF"> </snip>
LC Metadata Object Description Schema
MINERVA MODS Display
Top-Level MODS<mods:mods> <mods:titleInfo> <mods:title>Website of the APGA Women</mods:title> </mods:titleInfo> <mods:genre>Web site</mods:genre> <mods:originInfo> <mods:dateCaptured encoding="iso8601">20030417</mods:dateCaptured> </mods:originInfo> <mods:language authority="iso639-2b">eng</mods:language> <mods:physicalDescription> <mods:internetMediaType>text/html</mods:internetMediaType> <mods:internetMediaType>image/jpg</mods:internetMediaType> <mods:internetMediaType>image/gif</mods:internetMediaType> <mods:internetMediaType>application/msword</mods:internetMediaType> <mods:internetMediaType>application/x-shockwave-flash</mods:internetMediaType> </mods:physicalDescription> <mods:abstract>Supports the All Progressive Grand Alliance political party (APGA). Information on the APGA presidential candidate, Chief Chukwuemeka Odumegwu-Ojukwu. Based in Kennesaw, Georgia.</mods:abstract> <mods:subject> <mods:topic>Political Parties</mods:topic> <mods:geographic>Africa</mods:geographic> <mods:geographic>Nigeria</mods:geographic> </mods:subject> <mods:relatedItem type="host"> <mods:titleInfo> <mods:title>CRL Political Web Archiving Project</mods:title> </mods:titleInfo> <mods:identifier type="uri">http://www.crl.edu/content/PolitWeb.htm</mods:identifier> </mods:relatedItem> <mods:identifier displayLabel="Archived site" type="uri">http://dlibdev.nyu.edu/webarchive/metstest/apgawomen/20030417/www.agpawomen.org /</mods:identifier> </mods:mods>
Page-Level MODS
<METS:dmdSec ID="DM1"> <METS:mdWrap MDTYPE="MODS">
<METS:xmlData> <mods:mods>
<mods:titleInfo><mods:title>officers</mods:title>
</mods:titleInfo><mods:originInfo>
<mods:dateCaptured>20030417223125</mods:dateCaptured></mods:originInfo><mods:identifier type="uri">www.apgawomen.org/officers.htm</mods:identifier><mods:physicalDescription>
<mods:extent>3252</mods:extent></mods:physicalDescription>
<mods:genre>Web page</mods:genre></mods:mods>
</METS:xmlData> </METS:mdWrap></METS:dmdSec>
<METS:amdSec> <METS:techMD>
Technical Metadata Sources (.arc)
• Crawler frontier application– metadata about the harvest itself, the archive file
• Host server’s HTTP response headers– metadata about the host server, files
• Captured files themselves– file headers; IPTC headers -- human input– Post-processing with ImageMagick etc.
ImageMagick dump for Mao1925.jpg
Image: Mao1925.jpgFormat: JPEG (Joint Photographic Experts Group JFIF format)Geometry: 142x185Class: DirectClassType: true colorDepth: 8 bits-per-pixel componentColors: 11423Resolution: 300x300 pixelsFilesize: 8115bInterlace: PlaneBackground Color: grey100Border Color: #DFDFDFMatte Color: grey74Iterations: 0Compression: JPEGsignature:8c173bd33c3e5667d27e51aee539afcd58ccbc8d4a11ab76b127408905f598fdTainted: False
NISO Metadata for Images in XML Schema (MIX)
<mix:mix> <mix:BasicImageParameters> <mix:Format> <mix:MIMEType>image/jpeg</mix:MIMEType> <mix:ByteOrder>little-endian</mix:ByteOrder> <mix:Compression> <mix:CompressionScheme>5</mix:CompressionScheme> <mix:CompressionLevel>0</mix:CompressionLevel> </mix:Compression> <mix:PhotometricInterpretation> <mix:ColorSpace/> </mix:PhotometricInterpretation> </mix:Format> <mix:File> <mix:ImageIdentifier>perso.magic.fr/images/Mao1925.jpg</mix:ImageIdentifier> <mix:FileSize>8115</mix:FileSize> </mix:File> <mix:PreferredPresentation/> </mix:BasicImageParameters> <mix:ImageCreation/> <mix:ImagingPerformanceAssessment> <mix:SpatialMetrics> <mix:ImageWidth>142</mix:ImageWidth> <mix:ImageLength>185</mix:ImageLength> </mix:SpatialMetrics> <mix:Energetics> <mix:BitsPerSample>8</mix:BitsPerSample> </mix:Energetics> </mix:ImagingPerformanceAssessment> <mix:ChangeHistory/> </mix:mix>
Web Archiving Challenges III:Structuring and Managing Versions
Version control-related storage and access issues in a continuous archive:
• Creator-driven changes: successive harvests and versions
• Repository-driven changes: refreshing, migration, other changes
Modeling Website Objects with METS in a Continuous Archive
One possibility:
• Root level METS (web site X as intellectual object) with <mptr>s down to
• Intermediary METS (web site X as harvested on April 17, 2003) with <mptr>s down to
• Leaf node METS (single web page in web site X harvested on April 17, 2003)
APGA Women Websites
April 17, 2003 December 12, 2003 February 2, 2004
homeabout
officers
home
officers officers
about abouthome
news
APGA Women Websites
April 17, 2003 December 12, 2003 February 2, 2004
Aggregator / Single Capture Model
• METS for top level aggregation that uses <mptr>s to point to either another intermediary aggregator or to more than one captured version of a web site.
• METS for single standalone captured site, whether part of successive harvests or a one-off capture.
METS Website Aggregator
• Contains single MODS record describing the aggregation as an intellectual object– e.g. Election 2004; JohnKerry.com (Nov 1-10)
• Contains no amdSec, fileSec or structLink• Contains a root <div> for the aggregation
– nesting <div>s with <mptr>s to each subsidiary aggregation or captured version
MINERVA Election 2004
Kerry
Nader
Bush
Nov 1
Nov 2
Nov 3
Nov 1
Nov 2
Nov 3
Nov 1
Nov 2
Nov 3
MINERVA Election 2004
November 1, 2004November 2, 2004
November 3, 2004
Kerry
Bush
NaderKerryNader
Bush
Kerry Nader
Bush
Web Archiving Challenges IV:
Keeping archived websites hermetically sealed
How websites escape from archives
• External links
• Internal links not parsed out of FLASH
• Internal links not parsed out of javascript
• .php files not converted to static HTML
• .js runners or applets with date() functions
Sealing the archive
• What Crawlers Can Do
– rewrite internal links to relative links– repair producer-generated relative links– leave external links live? Or create custom 404s?– rewrite dynamic extensions e.g. .php to .html– successfully parse out javascript, FLASH URLs
Sealing the Archive
• What Applications can do:
– PANDAS– METS Viewer
PANDORA Treatment of External Links
<h1>External Links to African Websites</h1> <p><b>African News links:</b> <a href="/external.html?link=www-sul.stanford.edu/depts/ssrg/africa/news.html"><br> Latest African news</a><br> <a href="/external.html?link=kahn.interaccess.com/intelweb/africa.html">More African news sources</a></p> <p><b>General comprehensive resource links on Africa: </b><a href="/external.html?link=www.columbia.edu/cu/libraries/indiv/area/Africa/"><br> Columbia University - African Studies Internet Resources</a> <a href="/external.html?link=www-sul.stanford.edu/depts/ssrg/africa/guide.html"><br> African South of the Sahara internet resources</a><br> <a href="/external.html?link=www.sas.upenn.edu/African_Studies/Home_Page/AFR_GIDE.html"> Electronic Guide for African Resources on the Internet - University of Pennsylvania</a><br> <a href="/external.html?link=www.africa.com/">Africa.com</a><br> <a href="/external.html?link=www.sourceafrica.com/">Source Africa</a><br> <a href="/external.html?link=www.africapolicy.org/">African Policy Information Centre</a><br> <a href="/external.html?link=www.cc.utah.edu/~pks1019">University of Utah - Africa Homepage</a> <br> <a href="/external.html?link=www.fordham.edu/halsall/africa/africasbook.html">African History Internet Sourcebook</a><br>
METS Viewer
METS Viewer External Links